Metallurgical process



Feb; s, 1924. V, 1,483,056 W. E. GREENAWALT METALLURGICAL PROCES S vFiled Dec. 6. 1921 Patented Feb. 5, 1924.

UNITED STATES WILLIAM E. GREENAWALT, OF DENVER, COLORADO.

METALLURGICAL PROCESS.

Application filed December 6, 1921. `S era1 No. 520,241.

T 0 all whom it may concern.'

Be it known that I, WILLIAM E. GREENA- WALT, a citizen of the UnitedStates, residing in the city and county of Denver and State of Colorado,have invented 'certain new and useful Improvements in MetallurgicalProcesses, of which the following' is a specification.

The invention refers more particularly to the hydrometallurgicalextraction of copper from its ores, and has as its particular obiect theeconomical treatment of both oxidized and sulphide ores of copper bycombining the treatment of both into one readvisable, with ordinary acidleaching.

In leaching low grade oxidized ores, it usually takes from three to ivepounds of acid to extract one pound of copper; `If iron is used as theprecipitant, it willusually take from one to two pounds of iron, perpound of eopper'precipitated. Excess acid is neutralized at the expenseof the iron, so that where there is an appreciable amount of excessacid, both excess acid and iron are wasted. Then, too, the resultingcement copper is quite impure and has to be treated much the saine as ahigh grade copper ore, or concentrate, to obtain inerchantable copper.

It is evident, that with the consumption of from three to five pounds ofacid and from one to two pounds of iron, per pound of copper extracted,and with the copper in the form of an impure metal, the process becomesprohibitive. Acid plants are expensive to install, and even if installedon a small scale, the cost of acid is excessive. If the acid ispurchased, it will usually cost not less than 1.5 to 2.0 per pound,delivered at the mine.

One of the most difficult problems, in leaching copper ores, has been toovercome this acid expense. yThis difficulty is solved by the presentinvention, and one of the principal objects of this invention is ltoprovide sufficient acid, by a regenerative process, in the treatment ofoxidized and sulphide ores to make the process self sustaining in acidfor both.

Usually, sulphide and oxide ores occur in the same deposit. The oxidesoccur at or near the surface, the sulphides at depth, and a mixture ofboth in the intermediate zone. The oxides and sulphides may come fromthe same mine, or from different mines: the origin of the ore, for thepurpose of this invention, is immaterial.

As a preliminary to the description of the present process, it might-beWell to consider some matter bearing directly on it. In

carrying out the processes described in my Patents, No. 1,314,742,September 2, 1919, and No. 1,353,995, September 28, 1920, it was foundthat 1.4 lbs. of copper could be deposited per k. w. h., with thesimultaneous regeneration of 3.0 lbs. of acid, from a solutioncontaining as much, or more than 3.0% iron. It was also found that witha solution containingv 4.0% copper and 3.0% iron, the copper could bereduced to 1.0%, and the acid could be regenerated up to as high as10.0%, before it was necessary to return the solutionto the ore. Theferrie salts in the solution were under vgood control, and it was thiscontrol which made these results possible.

It was also found, by carefully roasting ya sulphide concentrate,containing, say, 15.0% copper, and roasting as described in my pendingapplication, Serial No. 485,885, filed July 19, 1921, that from to 75%of the copper could be made soluble in water, as the copper sulphate.The remaining copper in the roasted concentrate, is soluble, to a veryhigh percentage, in dilute acid, with an 'acid consumption not greatlyexceeding the theoretical, or practically, about 1.75 lbs. of acid` perlb. of copper so extracted. The excess acid produced, with a concentratecontaining 300 lbs. of extractible copper. with 50% of the copper in theroasted concentrate soluble in water,` would be about as follows:

` Lbs. acid.

300 lbs. copper 3.0 lbs. acid, per lb 900 150 lbs. copper 1.75 lbs. acidconsumed 263 Excess acid, per ton concentrate 637 This excess acid isthen applied to the oxidized ore. It is evident that vabout 13 tons oflow grade oxidized ore, Vcontaining 2.0% copper, and with an acidconsumption of 3.0 lbs. of acid, per lb. of copper, could be treatedwith this excess acid. It is believed that over 20 tons of oxidized orecould be treated, in the treatment of one ton of concentrate, if thecopper extracted from f I 20 tons of 2% oxidized ore, with acidregenerated in the regular operation of the process, with the use of thesulphur dioxide gas from the roasting furnace as a reducing Q agent.

The present process will now be described, reference may be made to theaccompanying flow sheet, in diagrammatic plan.

l The mixed sulphide and oxide ore is concentrated in the usual Way toseparate the sulphides from the oxides. The oxide tail ing, or ore, 'ischarged into a leaching vat, Where it may be treated either by agitationor percolation, preferably by percolation,

- if the ore can be leached effectively in that way. The sulphideconcentrate, containing about 15% extractible copper, is sent to theroasting furnace, where it is roasted at a low temperature, to make asmuch as possible of the copper soluble in water. Usually there will beno difliculty in making from 50% to 75% of the copper in the roastedconcentrate soluble in water. The roasted concentrate is then leached,preferably, by agitation, on account of its high grade. The resultingcopper solution will be fairly high in both copper and iron: and may beassumed to contain about 4.0% copper and 3.0% iron. The amount of ironin the copper solution is quite immaterial, in the operation of thisprocess, for the reason that by t-he use of sulphur dioxide, asindicated, the iron can be maintained quite closely in the ferrouscondition, and this is of importance. The solution from the copperconcentrate leaching tank is flowed into a closed chamber, designated asS()2 reducer, No. 1, where thesulphur dioxide gas from the roastingfurnace is applied to it. The sulphur dioxide gas reduces the ferriesalts to the ferrous condition. The solution is maintained in a pool inthe SO2 reducers. The gas is maintained over the pool. The reducer isarranged so that the liquid in the pool may be treated with the gasconfined over it. The reduction of the ferrie salts is not a rapidreaction, with sulphur dioxide, and this arrangement provides sufiicienttime for effective work. The reduced solution flows into the settlingtank, where the solution is clarified, after which it is flowed throughthe electrolytic units. These units consist, essentially., of an SO2reducer and a number of electrolytic copper depositing cells, arrangedso that a continuous iow of reduced electrolyte, or solution, may bemaintained from the reducer to the cells and a return flow of oxidizedelectrolyte from the cells to the reducer. The copper solution is owedfrom the settling tank into the copper electrolytic cells, No. 1, wherea portion of the copper is deposited and acid and ferrie saltsregenerated. The flow is regulated so that the outflow from the cellswill not, preferably, exceed 0.25% ferric iron. The ferrie iron mayconveniently be less. A flow of reduced solution is maintained from thereducer to the cells, and a return flow of oxidized solution from thecells to the reducer, while a portion of the solution, the advance flow,is advanced to reducer No. 2, and from reducer No. 2, to the second setof electrolytic copper depositing cells, where, again, a portion of thesolution is circulated between the reducer and the cells, While anotherportion is returned to the roasted concentrate, and another portion, theadvance flow, is applied to the oxidized ore in the leaching tank. Thecopper in this solution, as returnedto the con centrate and as advancedto the oxidized ore, will amount to about 1.0% and the acid may be from5.0% to 10.0%. In this way the copper concentrate is treated until thecopper is suiiiciently extracted, and the leach tailings wasted.

The regenerated acid, or advance solution, is applied to the ore in theoxidized ore leaching tank, where copper and soluble impurities aredissolved, and the acid practically neutralized, so that the resultingsolution contains considerable copper, and somewhat more iron and otherimpurities. This solution is then treated with sulphur dioxide inreducer No. 3, and flowed into the third series of electrolytic cells.As before, a portion of the electrolyzed solution is returned to thereducers, while another portion, the advance flow, is owed'into reducerNo. 4, where it is again treated with sulphur dioxide, and thenelectrolyzed in the fourth series of electrolytic cells. The solution,issuing from the last series of electrolytic cells, will containconsiderable regenerated acid, some ferric iron, and a small percentageof copper', usually from 0.25% to 0.50%. A portion of this solution isreturned to the oxidized ore leaching vat, while another portion, theadvance How, or a portion of it, is passed on tothe chemical copperprecipitator, where the small remaining amount of copper is precipitatedchemically out of the solution, and the solution wasted. vAny method ofchemically precipitating the copper from the waste solution may be used.'Hydrogen sulphide is preferred, for the reason that the copper iseffectively precipitated from acid solutions with hydrogen sulphide,whereas, other precipitants, such as metallic iron, act on t e acid aswell as on the copper, and this would require a large amount ofprecipitant per unit of copper precipitated. Water is necessarily addedto the solution in amounts at least equal to the quantity of foulsolution wasted: a large portion of this fresh water is convenientlyadded to the solution from the moisture in the oxidized ore in theoxidized ore leaching tank, and wash waters resulting from washing theleached residues of both the roasted concentrates and oxidized ore.

The sulphur gas from the roasting furnace is preferably passed throughthe respective reducers, in series, as shown, by means of an exhaustercommunicating with the last reducer. The order of the reducers is not ofgreat importance, so far as the application of the sulphur gas isconcerned, altho it is preferred to apply the strongest gas, direct fromthe roaster, to the fresh copper solution, or the solution flowing fromthe roasted sulphide concentrates. This method of operation keeps thedissolved impurities within workable limits. The amount of impuresolution wasted will be mostly determined by the amount of soluble iron,but, as the electrolysis, under the conditions, is practicallyindependent of the amount of iron in the electrolyte, the iron contentmay be maintained quite high, and this means that the amount of solutionwasted may be kept relatively small.

The control of the ferrie salts is a vital factor in the operation ofthe process. By maintaining a flow of reduced solution from the reducerto the electrolyzers, and of oxidized, or electrolyzed, solution fromthe cells to the reducers, while advancing a portion of the solutionthrough the entire system, the ferrie salts may be kept at a very lowlimit, usually considerably below 0.25% ferrie iron, and this serves toget a high energy efficiency, a high acid regeneration, and 'freedomfrom annoyances invariably accompanying high ferrie iron in theelectrolyte.

A ttention is called to the desirability of having a fairly strong acidsolution, especially in the leaching of concentrate. ln the ordinaryoperation of electrolytic processes, the ferrie salts accumulates sorapidly in the electrolyte, and its presence is so harmful, that a highregenerated acid solution is diiiicult, and in fact, quite impractical.A low acid solution greatly complicates the leaching operation. A highacid solution greatly simplifies it.

By the operation of this process, the fol lowing results may beexpected: First, the deposition of about 1.4 lbs. of copper, per k. w.h. (E. M. F. measured across the bus bars of the cells) Second, use ofthe SO,

from the roasting furnace, as a reducing agent for the ferric saltsformed, with the regeneration of 3.0 lbs. of acid, per lb. of copperdeposited: Third, the regeneration of suiicient acid in the entireoperation of the process itself to make it self-sustaining in acid forthe treatment of one ton of 15% copper sulphide ore or concentrate, andfrom fifteen to twenty tons of about 2.0% oxidized copper ore, asindicated. This will ordinarily come within the range of the treatmentof copper ores which are amenable to acid leaching.

The SO2 reducer-s may conveniently be made as shown in my Patent, No.1,353,995, September 28, 1920; or as shown in my pending application,Serial No. 485,884, filed July 19, 1921. The reducer consists,essentially, of a covered chamber adapted to contain a. pool of liquidand to confine a gas over the pool, and arranged so that the liquid ofthe pool may be treated `with the gas. This may be done by spraying theliquid of the pool into the gas, which saturates, or supersaturates thefine liquid spray, and this spray falling into the pool, also saturates,or absorbs the gas in the liquid in the pool, so that the entire liquidof the pool is under the action of the gaseous reducing agent. Asrapidly as the gas in the pool reacts with the liquid, fresh gas isabsorbed due to the liquid spray. This, effectively, brings in theelement of time, so essential in the reduction of ferrie salts withsulphur dioxide. It maintains the entire pool of liquid under continuoustreatment with the gas. The liquid flows into the pool at one end andout of the pool at the other end. The time factor is dependent on thesize of the pool.

It is desirable to apply the impure gas (gas containing dust etc.) fromthe roaster` to the impure copper solution from the leaching tank oragitator. By this arrangement the gas is washed and purified for thesubsequent reducers, and by allowing the reduced solution to settle, theimpurities in the solution are also eliminated for subsequentelectrolysis in the various series of cells. Practice has shown thatthere is no dificulty in passing the gas through the various reducers inseries, by means of an exhauster communicating with the last reducer.The suction is always inwardly and fumes do not esca-pe to contaminatethe surrounding atmosphere.

The pools of solution, or electrolyte, in the reducers are preferablyfairly large. The definite amount of electrolyte in the pools will bedetermined by the amount of reduction of the ferrie salts desired. Theferrie salts should be very effectively reduced to get good, or thebest, results in the electrolyzers. n

The process is advantageously applied to low grade roasted sulphide ore,instead of the oxidized ore in the oxidized ore leaching.

. tended to limit it to this application.

The process has been described particu-- larly in reference to sulphatesolutions. lt is also applicable to chloride and other solutions.

This application is intended to cover, in part, the process disclosed inmy apparatus patent 'referred to, No. 1,353,995, Septemher 28, 1920.

I claim:

1. A process of treating sulphide and oxide ores of copper comprising,treating the sulphide ore to get a sulphide concentrate, roasting theconcentrate, leaching the roasted concentrate With a dilute acidsolution, treating the resulting copper solution with sulphur dioxideobtained from roasting the sulphide concentrate, electrolyzing thesolution to deposit the copper and regenerate acid, returning a portionof the regenerated solution to the roasted concentrate to extract ltheremaining copper, applying the excess regenerated acid solution to theunrcasted oxidized ore to extract the copper therefrom, precipitatingthe copper from the resulting solution obtained from leaching theunroasted oxidized ore, and then Wasting the solution.

2. A process of treating sulphide and oxide ores of copper comprising,concentrating the sulphide ore to obtain a concentrate relatively highin copper and sulphur, roasting the concentrate to make a portion of thecopper soluble in Water and a portion soluble in dilute acid, leachingthe roasted concentrate With a dilute acid solution, treating theresulting copper solution with sulphur dioxide obtained from roastingthe sulphide concentrate, electrolyzing the solution to deposit thecopper and regenerate acid, returning a portion of the regenerated acidsolution to the roasted concentrate, applying the excess regeneratedacid solution to the unroasted oxidized ore to extract the coppertherefrom, precipitating the copper from the resulting solution with thesimultaneous regeneration of acid, returning a portion of theregenerated acid solution to the unroasted oxidized ore, and discardinganother portion.

3. A process of treating sulphide and oxide ores of copper comprising,treating the sulphide ore to obtain a concentrate relatively high incopper and sulphur, roasting the concentrate to make a portion of thecopper soluble in Water and a portion soluble in dilute acid, leachingthe roasted concentrate with a dilute acid solution, treating theresulting solution with sulphur dioxide, electrolyzing the solution todeposit the copper and regenerate acid, returning a portion of theregenerated acid solution to the roasted concentrate, applying theexcess acid solution to the unroasted oxidized ore to extract the coppertherefrom, precipitating the copper' from the resul-ting solution withthe simultaneous regeneration of acid, returning a portion of the foul.re enerated acid solution to the unroasted oxi ized ore,y anddiscarding another portion.` y

4. A process of treating sulphide and oxide ores of copperI comprising,treating the sulphide ore to obtain a concentrate higher in copper andhigher in sulphur than the original ore, roasting the concentrate tomake a portion of the copper `soluble in Water and a portion soluble indilute acid, leaching the roasted concentrate with a dilute acidsolution, treating the resulting copper solution with sulphur dioxide,elec` trolyzing the solution to deposit the copper and regenerate acid,returning a ortion of the regenerated acid solution to t e roastedconcentrate, applying the excess acid to the unroasted oxidized ore toextract the copper therefrom, applying sulphur dioxide to the resultingcopper solution, precipitating the copper from the solution with thesimultaneous regeneration of acid, returning a portion of the resultingfoul regenerated acid solution to the unroasted oxidized ore, anddiscarding another portion.

5. A process of treating sulphide and oxide ores of copper comprising,roasting the sulphide ore to makel a portion of the copper soluble inWater and another por- 100 tion soluble in dilute acid, leaching theroasted ore with a dilute acid solution, treating the resulting coppersolution with a reducing agent, electrolyzing the solution to depositthe copper and regenerate acid, returning a portion of the regeneratedacid solution to thev roasted ore, applying another portion to theoxidized ore, applying a reducing agent to the resulting copper solutionfrom the oxidized ore, precipitating the copper therefrom with thesimultaneous regeneration of acid, returning a portion of theregenerated acid solution to the oxidized ore, and discarding anotherportion so that by adding an equivalent of Water to the leach solutionthe impurities in the solution may be maintained Within desired limits.

6. A process of treating sulphide and oxide ores of copper comprising,treating the sulphide ore to obtain a sulphide concentrate, roasting theconcentrate to make a portion of the copper soluble in Water and anotherportion soluble in dilute acid, leaching the roasted concentrate with aVdilute acid solution, treating the resulting copper solution with thesulphur dioxide obtained from roasting the sulphide concentrate,electrolyzing the solution to deposit the cop per and regenerate acid,returning a portion of the regenerated acid solution to the Vil()roasted concentrate, applying another portion to the unroasted oxidizedore, treating the solution from the unroasted oxidized ore with sulphurdioxide obtained from roasting the sulphide concentrate, precipitatingthe copper from the resulting solution With the simultaneousregeneration of acid, returning a portion of the regenerated acidsolution to the unroas'ted oxidized ore, and discarding another portion.

T VA process of treating sulphide and oxide ores of copper comprisingroasting the sulphide ore to make a portion of the copper soluble inWater and another portion soluble in dilute acid, leaching the roastedore with a dilute acid solution, treating the solution with sulphur gasobtained from roasting the sulphide, electrolyzing the solution todeposit the copper vyith the simultaneous regeneration of acid,returning a portion of the regenerated acid solution to the roasted ore,applying another portion to the oxidized ore, applying a reducing agentto the resulting copper solution from the oxidized ore, electrolyzingthe solution to deposit the copper and regenerate acid, returning aportion of the resulting foul acid solution to the oxidized ore, anddiscarding another portion.

8. A process of treating sulphide and oxide ores of copper comprising,roasting the sulphide ore, leaching thev roasted ore With a dilute acidsolution to extract the copper, applying a reducing agent to the coppersolution, electrolyzing the reduced solution and repeating the cycle ofalternate reduction and electrolysis until the solution is suiiicientlydepleted in copper and regenerated in acid, then returning a portion ofthe regenerated acid solution to the roasted ore, applying anotherportion to the. oxidized ore, precipitating the copper from the solutionobtained from the oxidized ore, and discarding the solution.

9. A process of treating sulphide and oxide ores of copper comprising,roasting the sulphide ore,"leaching the roasted ore with a dilutesolution of acid, treating the resulting copper solution containingsalts of iron with the sulphur dioxide obtained from roasting thesulphide, electrolyzing the solution to deposit the copper andregenerate acid and repeating the cycle of reduction and electrolysisuntil the solution is suiiiciently depleted in copper and regenerated inacid, then returning a portion of the regenerated acid solution to theroasted ore to complete the extraction of the copper and applyinganother portion to the oxidized ore to extract the copper therefrom,treating the resulting copper solution from the oxidized ore with thesulphur dioxide obtained from roasting the sulphide ore, electrolyzingthe solution to deposit the copper and regenerate acid and repeating andelectrolysis until the solution is suiiicientiy depleted in copper andregenerated in acid, then returning a portion of the regenerated acidsolution to the roasted ore and applying another portion to the ox-,l

idized ore to extract the copper therefromf treating the resultingcopper solution from the oxidized ore with the sulphur dioxide obtainedfrom roasting the sulphide ore, electrolyzing the solution to depositthe copper and regenerate acid and repeating the' cycle of reduction andelectrolysis until the solution is sufficiently depleted in copper andregenerated in acid, then returning a portion or' the regenerated acidsolution to the oxidized ore, chemically precipitating the small amountof remaining copper from another port-ion and discarding the resultingbarren solution.

11. A process of treating sulphide and oxide ores of copper comprising,roasting the sulphide ore, leaching the roasted ore With a dilute acidsolution, applying sulphur dioxide to the resulting copper solution,electrolyzing the solution to deposit the copperr and regenerate acid,.cycl'ically circulating a portion ot the regenerated acid solutionbetweenthe roasted ore the sulphur dioxide reducer and the electrolyzeruntil the copper in the ore is suiiiciently extracted, advancing anotherportion of the regenerated acid solution 'to the oxidized ore tovextract the copper therefrom, applyingl sulphur dioxide to the resultingsolution from vthe oxidized ore, precipitating the copper from thesolution With the simultaneous regeneration of acid, returning a portionof the regenerated acid solution to the ore and discarding anotherportion.

12. A process oic treating sulphide and oxide ores of copper comprising,treating the sulphide ore to obtain a sulphide concentrate, roasting thesulphide concentrate to make a relatively large portion of the coppersoluble in Water, leaching the copper from the roasted concentrate witha dilute. acid solution, applying the sulphur dioxide from the roastingconcentrate to the resulting copper solution, electrolyzing the solutionto deposit the copper and regenerate acid, and

` trolyzing the solution to deposit .the copper and regenerate acid,returning a portion of the regenerated acid solution to lthe roastedconcentrate to complete the extraction otI the copper, and` applying theexcess acid solution tothe unroasted oxidized ore to extract the coppertherefrom.

14. A process of treating sulphide and oxide ores of copper comprising,treating the sulphide ore to obtain a sulphide concentrate, roasting thesulphide concentrate, leaching the roasted concentrate with a dilute`acid solution. to extract a portion ot' the coppe-napplying sulphurdioxide obtained from roast-lng the sulphide concentrate to the coppersolution containing salts ot iron to 'reduce the ferrie salts to theferrous condition, electrolyzing thesolution to deposit the copper andregenerate acid and ferric salts, circulating a portion of the solutionin a vclosed circuit between the reducer and electrolyzer andalternately subjecting it to reduction and electrolysis, and then whenthe solution is sufficiently depleted in copper and regenerated in acidreturning a portion of lthe regenerated acid solution to the roastedconcentrate and applying the excess acid to the unroasted oxidized oreto extractthe co per therefrom.

15. n the electrolysis ot copper solutions obtained from leaching oresand containing salts of iron, a process comprising, a progressivelyadvancing the solution through a series of electrolytic units comprisinga reducer and electrolyzer, circulating a portion of the solution in itsadvance tlow between vthe reducers and electrolyzers ot itherespeccontaining salts of iron, a process comprising progressivelyadvanoi ng ithe solution through a 'serieslof electrolytic unitscomprising a. reducer vand electrolrzer, circulating a por tion of the`solution between. the electr-olv fr and reducer ot one electr-olyticunit and a terna'tely subjectingit to 'reduction and electrolysis, andadvancing a portion to another elcctrolyt-ic unit and repeating thecycle until the solution is suiliciently dep `cited in copper andregenerated in acid, and then returning the regenerated acid solution tothe ore 17. A process of treating ores of copper comprising, leachingthe ore to extract the copper, progressively advancing the resultingcopper solution containing salts ot iron through a series otelectrolytic units coniprising a reducer and an elcctrolyzer,subjee-ting the solution alternately to the action oit electrolysis andto the action of sulphur dioxide in the reducers in the respectiveelectrolytic units, progressiiv'ely advancing the sulphur dioxidethrough the respective reducers, circulating a port-ion oi the so lutionin closed circuit between the reducers and electrolyzers of oneelectrolytic unit and advancing another portion to the next electrolyticunit o't' the series and repeating t-he cycle until the solution issufficiently depleted in copper and regenerated in acid and thenreturning the regenerated acid solution to the ore.

18. A process of treating ores of copper comprising leaching the ore toextract the copper, passing the resulting copper solution containingsalts of iron through a series ot electrolyzers, passing the coppersolution through a series of pools of the solution so that theinflow/ing solution Will mingle With the pool, treating the solutions otthe pool with sulphur dioxide, circulating a portion ot' the solution ina closed circuit between the respective pools and electrolyzers, andprogressively advancing a portion of the solution. through the series ofpools and electrolyzers until the solution is sufficiently depleted incopper and regenerated in acid and returning the regenerated acidsolution to the ore.

19. A processof treating orcs oit copper comprising, leaching lthe oreWith a dilute acid solution, alternately subjecting the solutioncontaining salts of iron to the action of sulphur dioxide and to theaction of the electric current in a series ot reducers andelectrolyzers, progressively advancing a portion ot the solution fromone series of reducers and electrolyzers to the next until the solutionis sufficiently depleted in copper and regenerated 'in acid, and thenreturnin the rogruinerated acid solution to the ore.

20. A process ot treating copper ores comijirising, leaching the oreWith a dilute acid solution, alternately subjecting the resulting coppersolution containing salts of iron to the action ot sulphur dioxide' andto the action of the electric current in a series ot reducers andelectrolyzers, and progressively advancing the sulphur dioxide from onereducer to the next olf the series.`

2l. A process of treating copper ores comprising, leaching the ore witha dilute acid solution, alternately subjecting the resulting coppersolution containing salts of iron to the action of sulphur dioxide andto the action of the electric' current in a closed circuit in a seriesof electrolytic units containing a reducer and an electrolyzer,progressively advancing a portion of the solution from one electrolyticunit to the next of the series, and when the solution is sufficientlydepleted in copper and regenerated in acid, returning the regeneratedacid solution to the ore.

22. A process of treating ores of copper comprising, leaching the orewith a dilute acid solution, alternately subjecting the resultingsolution containing salts of iron to the action of a gaseous reducingagent and to the action of the electric current in a closed circuit in aseries of electrolytic units containing a reducer and electrolyzer,progressively advancing a portion of the solution from one electrolyticunit to the next of the series, and when the solution is sucientlydepleted in copper -and regenerated in acid returning the regeneratedacid solution to the ore.

23. A process of treating copper ores comprising, leaching the ore With.a dilute acid solution, alternately subjecting the resulting coppersolution containing salts of iron to the action of a reducing gas and tothe action of the electric current in a closed circuit in a series ofelectrolytic units containing a reducer and an electrolyzer,progressively advancing a portion of the solution from one electrolyticunit to the next of the series, and progressively advancing the reducinggas from one reducer to the next of the series.

24. A process of treating copper ores comprising, leaching the ore witha dilute' acid solution` electrolyzing the resulting copper solutioncontaining salts of iron to deposit the copper with the simultaneousregeneration of acid and ferrie salts, reducing the 'lerric salts formedby the electrolysis to the ierrous condition by applying sulphur dioxideto a series of pools of the solution alternating with the electrolyzers,progressively advancing the solution through the series ofelectrolyzers, progressively advancing the solution through the seriesot pools of the electrolytev` and treating the electrolyte of the poolswith the sulphur dioxide.

25. A process of treating cop-per ores comprising, leaching the ore Witha dilute acid solution, electrolyzing the resulting copper solutioncontaining salts of iron to deposit the copper and regenerate acid andferrie salts, reducing the ferrie salts formed by the electrolysis byapplying a reducing gas to a series of relatively large pools of thesolution alternating With the electrolyzers,

progressively advancing the solution through the series ofelectrolyzers, progressively advancing the solution through therelativeljv large pools of the electrolyte and treating` the electrolyteof the pools with a reducing gas, and When the solution is sufficientlydeplet-ed in copper and regenerated in acid returning the regeneratedacid solution to the ore.

26. A process of treating mixed sulphide and oxide ores of coppercomprisings crushing the ore, separating the sulphide from the oxide,roasting the sulphide, leaching the roasted ore with dilute acidsolution, treating the resulting copper solution with the sulphurdioxide obtained from roasting the sulphide, electrolyzing the solutionand repeating the cycle of reduction and electrolysis until the solutionis suiciently depleted in copper and regenerated in acid, and thenapplying the regenerated acid solution to the oxidized ore to extractthe copper therefrom.

27. A process of treating copper ores comprising, leaching the ore witha dilute acid solution, flowing the solution through a series ofelectrolyzers to deposit the copper and regenerate acid and ferriesalts, maintaining a series of relatively large pools of the electrolytein communication with the electrolyzers, treating the electrolyte of thepools with sulphur dioxide, circulating a portion of the electrolyte ina closed circuit through the respective pools and electrolyzers, andprogressively advancing the electrolyte through the respective pools andelectrolyzers until the solution is suiiciently depleted in copper andregenerated in acid and then returning the regenerated acid solution tothe ore.

28. A process of treating copper ores comprising, leaching the ore witha dilute acid solution, passing the resulting copper solution through aseries of reducers and treating it therein with sulphur dioxide, passingthe solution through a series of electrolyzers to deposit the copper andregenerate acid and ferrie salts, circulating the solution in a closedcircuit between the respective reducers and electrolyzers of the series,progressively advancing the solution through the series of reducers andelectrolyzers until the solution is sufficiently depleted in copper andregenerated in acid, and when the solution is suiciently depleted incopper and regenerated in acid returning the solution to the ore.

29. A metallurgical process comprising treating copper ore with a diluteacid solution to extract the copper, alternately sub-A jecting theresulting copper solution containing salts of iron to the action ofsulphur dioxide in a series of reducers containing relatively largepools of the solution and vto the action of the electric current in aseries of electrolyzers. progressively advancing the solution from onereducer and electrolyzer to the next reducer and electrolyzer of theseries ot' reducers and electrolyzers until the solution is suflicientlydepleted in copper and regenerated in acid, and then returning theregenerated acid. solution to the ore.

BO. A metallurgical process comprising5 treating copper ore with adilute acid s0- lution to extract the copper, alternately subjecting theresulting copper solution containing salts of iron to the action of areducing gas and to the action of an electric current in a series ofreducers and electrolyzers, progressively advancing the Solution fromone reducer and electrolyzer to the next reducer and electrolyzer of theseries until the solution is suiiciently depleted in copper andregenerated in acid, and then chemically precipitating the remainingcopper from the electrolyzed solution With the simultaneous regenerationof acid.

31. A metallurgical process comprising treating copper ore vWith adilute acid `solution to extract the copper, alternately subjecting theresulting copper solution containing salts of iron to the action ofsulphur dioxide in a series of reducers containing relatively largepools of the solution and to the action of the electric current in aseries of electrolyzers, and progressively advancing the solution fromone reducer and electrolyzer to tlie next reducer and electrolyzer ofthe series of reducers and electrolyzers until the copper in thesolution is sulficiently depleted.

32. A metallurgical process comprising treating copper ore with a diluteacid solution to extract the copper, alternately subjecting theresulting copper solution con-l taining salts of iron to the action ofsulphur dioxide and to the action of an electric current in a series ofreducers and electrolyzers, progressively advancing the solution fromone reducer and electrolyzer to the next rei ducer and electrolyzer oi'the series until the solution is sufficiently depleted in copper andregenerated in acid and then returning the regenerated acid solution tothe ore.`

WILLIAM E. GREENAWALT.

